Field of the Invention
The present invention relates to a light source apparatus and a display apparatus.
Description of the Related Art
Some color image display apparatuses have color liquid crystal panels having color filters and light source apparatuses (backlight apparatuses) that emit white light to the back surfaces of the color liquid crystal panels.
Conventionally, a fluorescent lamp such as a cold cathode fluorescent lamp (CCFL) or the like has been mainly used as the light source of the light source apparatus. However, in recent years, a light-emitting diode (LED) excellent in terms of power consumption, life, color reproducibility, and environmental load is used increasingly as the light source of the light source apparatus.
The light source apparatus (LED backlight apparatus) that uses the LED as the light source usually has a large number of the LEDs. Japanese Patent Application Laid-open No. 2001-142409 discloses the LED backlight apparatus that has a plurality of light emission units each having one or more LEDs. In addition, Japanese Patent Application Laid-open No. 2001-142409 discloses that the brightness of the light emission unit is controlled for each light emission unit. By reducing the light emission brightness of the light emission unit that emits light to an area of a screen of a color image display apparatus in which a dark image is displayed, power consumption is reduced and the contrast of the image is improved. Such brightness control for each light emission unit corresponding to the feature of the image is called local dimming control.
When the spread of light from the light emission unit is suppressed, it is possible to increase the degree of improvement of the contrast by the local dimming control. Specifically, in the case where the leakage of light emitted from one light emission unit to the area corresponding to the other light emission unit is suppressed, it is possible to increase the degree of improvement of the contrast by the local dimming control. For example, as disclosed in Japanese Patent Application Laid-open No. 2006-339148, by surrounding the light source with a plurality of reflection units (conical reflection units), it is possible to suppress the spread of light from the light emission unit and increase the degree of improvement of the contrast by the local dimming control.
The light source apparatus has a problem that the light emission brightness of the light emission unit changes. The change of the light emission brightness occurs due to, e.g., the change of light emission characteristics of the light source caused by the change of temperature, the aged deterioration of the light source, and the like. In a light emission apparatus having a plurality of the light emission units, a variation in temperature or aged deterioration between the plurality of the light emission units causes a variation in light emission brightness (brightness variation) between the plurality of the light emission units.
As a method for reducing the change of the light emission brightness and the brightness variation, there is known a method in which the light emission brightness of the light emission unit is adjusted by using an optical sensor that detects light emitted from the light emission unit. Specifically, there is known the method in which the optical sensor that detects reflected light emitted from the light emission unit and reflected toward the light emission unit by an optical sheet (optical member) of the light source apparatus is provided, and the light emission brightness of the light emission unit is adjusted based on the detected value of the optical sensor. In the light emission apparatus having the plurality of the light emission units, the light emission units are turned on one by one successively and a process in which the reflected light is detected and the light emission brightness is adjusted is performed for each light emission unit. Such a technique is disclosed in, e.g., Japanese Patent Application Laid-open No. 2013-211176.